Using Electrochemical Impedance Spectroscopy to Study the in vivo Evolution of the Electrochemical Properties of Neural Implants

Electrochemical impedance spectroscopy (EIS) is widely used in biomedical technology, for instance to monitor the body composition of patients or for the electrochemical characterization Brain-Computer Interfaces (BCI). When a neural implant is placed within a body, its EIS is modified by the interaction of the material with cells and by action of the biological tissue itself. Classical impedance meters are not practical for measurements on animal models and hence not suited for the in vivo follow-up of such BCI. The present study describes a portable device based on homemade electronic shields compatible with classical microcontrollers that can measure the EIS. EIS measurements concerning a subretinal diamond implant inserted chronically in the eye of a wild-type rat eye are performed with this custom impedance meter and presented here. This low-cost on-board wireless impedance meter can be used for a large range of applications.